System management

The z/OS operating system is designed to host many applications on a single platform. From the beginning, efficient management of the applications and their underlying infrastructure has been an essential part of the z/OS ecosystem. This chapter will discuss the regular system operations, monitoring processes, and tools you find on z/OS. I will also look at monitoring tools that ensure all our automated business, application, and technical processes are running as expected. System operations The z/OS operating system has an extensive operator interface that gives the system operator the tools to control the z/OS platform and its applications and intervene when issues occur. You can compare these operations facilities very well with the operations of physical processes like in factories or power plants. The operator is equipped with many knobs, buttons, switches, and meters to keep the z/OS factory running. Operator interfaces and some history By design, the mainframe performs operations on so-called consoles. Consoles originally were physical terminal devices directly connected to the mainframe server with special equipment. Everything happening on the z/OS system was displayed on the console screens. A continuous newsfeed of messages generated by the numerous components running on the mainframe streamed over the console display. Warnings and failure messages were highlighted so an operator could quickly identify issues and take necessary actions. Nowadays, physical consoles have been replaced by software equivalents. In the chapter on z/OS, I have already mentioned the tool SDSF from IBM or similar tools from other vendors available on z/OS for this purpose.  SDSF is the primary tool system operators and administrators use to view and manage the processes running on z/OS. Additionally, z/OS has a central facility where information, warnings, and error messages from the hardware, operating system, middleware, and applications are gathered. This facility is called the system log. The system log can be viewed from the SDSF tool. SDSF options Executing an operator command through SDSF The system log viewed through SDSF An operator can intervene with the running z/OS system and applications with operator commands. z/OS itself provides many of these operator commands for a wide variety of functions. The middleware tools installed on top of z/OS often also bring their own set of operator messages and commands. Operator commands are similar to Unix commands for Unix operating systems and functions provided by the Windows Task Manager and other Windows system administration functions. Operator commands can also be issued through application programming interfaces, which opens possibilities for building software for automated operations for the z/OS platform. Automated operations In the past, a crew of operators managed the daily operations of the business processes running on a central computer like the mainframe. The operators were gathered in the control room, also called a bridge, from where they monitored and operated the processes running on the mainframe. Nowadays, daily operations have been automated. All everyday issues are handled through automated processes; special software oversees these operations. When the automation tools find issues they cannot resolve, an incident process is…

Parallel sysplex

One of the most distinguishing features of the z/OS operating system is the way you can cluster z/OS systems in a Parallel Sysplex. Parallel Sysplex, or Sysplex in short, is a feature of z/OS that was built in the 90s that enables extreme scalability and availability. In the previous post we highlighted the z/OS Unix part. Here we will dive into the z/OS Parallel Syplex. A cluster of z/OS instances With Parallel Sysplex you can configure a cluster of z/OS operating system instances. In such a sysplex you can combine the computing power of multiple of z/OS instances on multiple mainframe boxes into a single logical z/OS server. When you run your application on a sysplex, it actually runs on all the instances of the sysplex. If you need more processing power for your applications in a sysplex, you can add CPUs to the instances, but you can also add a new z/OS system to the sysplex. This makes a z/OS infrastructure is extremely scalable. Also, a sysplex isolates your applications from failures of software and hardware components. If a system or component in a Parallel Sysplex fails, the software will signal this. The failed part will be isolated while your application continues processing on the surviving instances in the sysplex. Special sysplex components: the Coupling Facility For a parallel sysplex configuration, a special piece of software is used: a Coupling Facility. This Coupling Facility functions as shared memory and communication vehicle to all the z/OS members forming a sysplex. The z/OS operating system and the middleware can share data in the Coupling Facility. The type of data that is shared are the things that members of a cluster should know about each other since they are action on the same data: status information, lock information about resources that are accessed concurrently by the members, and caching of shared data from databases. A Coupling Facility runs in a dedicated special operating system, in an LPAR of its own, to which even system administrators do not need access. In that sense it is a sort appliance. A sysplex with Coupling Facilities is depicted below. There are multiple Coupling Facilities to avoid a single point of failure. The members in sysplex connect to the Coupling Facilities. I have not included all the required connections in this picture, as that would become a cluttered view. A parallel sysplex Middleware exploits the sysplex functions Middleware components can make use of the sysplex features provided by z/OS, to create clusters of middleware software. Db2 can be clustered into so-called Datasharing Group. In a Datasharing Group you can create a database that can process queries on multiple Db2 for z/OS instances on multiple z/OS systems. Similarly WebSphere MQ can be configured in a Queue Sharing Group, CICS in a CICSPlex, IMS in an IMSPlex and other software like WebSphere Application Server, IDMS, Adabas and other middleware use parallel sysplex functions to build highly available and scalable clusters. This concept is illustrated in Figure 15. Here you…

The Unix parts of z/OS

In the previous DBAOTM post I have introduced you to the z/OS operating system, the flagship operating system for the mainframe. In this post I will introduce you into the Unix side that z/OS has been equipped with over the past two decades. Since the 1990s IBM has added Unix functionality to z/OS. The first extension was z/OS Unix System Services – z/OS Unix in short - and recently we IBM have added z/OS Container Extensions. z/OS Unix The Unix part of z/OS is a runtime environment that is an integral part of the z/OS operating system. z/OS Unix is fully Unix (Posix) compliant. z/OS Unix provides an interactive command interface that is called a shell in Unix terminology. IBM has developed this part in the 1990s to make it easier to port applications from other platforms to z/OS. Many off-the-self and open source middleware and application packages that are available on z/OS make use of z/OS Unix. Examples are IBM’s own WebSphere Application Server and IBM Integration Bus, the banking product BASE24-eps from ACI, and open source tools like PHP and Git. z/OS Unix has regular files the same as other Unix systems. In the z/OS Unix shell you can use normal Unix commands like ls, cd, more and many more of the standard Unix commands. You can set up a telnet or SSH session with z/OS Unix and do many more things you can also do with other Unix environments. z/OS Container Extensions A very recent development on z/OS (it came with z/OS 2.4, end 2019) is the possibility to run Linux Docker Containers on z/OS. Docker containers are a hardware independent and lightweight manner to run many applications in a virtualized configuration. The Docker technology has been available on x86 platforms for a long time. With Docker containers you get a virtualization solution that does not need a complete virtual machine with an operating system running in it for every application. Instead your application is running in a small container that provides only a limited set of virtualization facilities. Just the things that the application needs. You can run many Docker containers – so applications – on a single real operating system image. The interesting thing is that in a conceptual way Docker is a quite like z/OS as we have seen it in section Address Spaces are processes. On a z/OS operating system you can run many applications in “Address Spaces”. With Docker you run many container processes on a single real operating system image. I will talk a bit more about Docker in section Linux in z/OS Container Extensions. z/OS Address Spaces versus Docker containers All Unix variants A small elaboration, as you may already get confused with the Unix on the mainframe. I mentioned Linux for the mainframe, now I talk about z/OS Unix and Linux in Containers. It is important to understand the difference between z/OS Unix, z/OS Container Extensions and Linux for Z. z/OS Unix and z/OS Container Extensions are an integral…

DBAOTM – z/OS – the mainframe flagship operating system

In the previous DBAOTM post I have described the operating systems available for the IBM mainframe and seen z/OS is the flagship in this category. In this post I will introduce you into the z/OS operating system concepts and terminology. The goal of this piece is to give you a good idea what is special about z/OS are and how the peculiarities relate to more commonly known concepts in Unix and Windows operating systems. z/OS: MVS and Unix combined I will describe the z/OS operating system into two parts, and discuss these separately. The traditional part is MVS and this part deviates most from what we know from Windows and Unix. The second part is z/OS Unix, an extension that can run Unix applications, very much similar to other Unix flavours. Next in my discussion, in upcoming posts about z/OS, I will talk about the unique clustering facility that z/OS brings, called parallel sysplex. Finally I will cover the green screens that the mainframe is often associated with, and discuss where this is still used. I will discuss modern tools and IDE’s for z/OS that come with modern user interfaces, replacing the old green-screen based tools. The MVS part of z/OS The MVS side of z/OS is the traditional mainframe side. This is the part that has its roots in the 1960s. MVS and its predecessors were built in the era in which batch processing with punch cards was the basic way of interacting with the mainframe. In MVS we find the features that today look a bit awkward. Basic operation of the MVS part with batch and JCL First let’s have a look at he basic operation of a batch process in z/OS. The batch process is core to the MVS part of z/OS. In essence, today it still works in the same way as it was when designed in the 1960. To run a program on z/OS you need to have a means to tell it what to do. You do this by creating a script, which is usually quite small. The language for this script is called JCL – Job Control Language. With the JCL script you tell the computer which program to run, and for that, what the input is for that program and where the output must be written to. This looks like a piece of code like this: //RUNPROG  EXEC PGM=PROGRAM1 //INPUT    DD DISP=SHR,DSN=MY.INPUT.DATA //OUTPUT   DD DISP=NEW,MY.OUTPUT.DATA This code looks awful of course, despite its simplicity. This is because the language was designed for punch cards. Punch cards can carry 80 characters per line, and every line also needed some special positions to control the operation of the punch card reader. Also, to make things as simple as possible for the punch card reader, everything is in uppercase. All in all, JCL is probably easily readable for a punchcard reader device, but from an aesthetical and ergonomic perspective it is horrendous. Anyway, with the above snippet of JCL you tell the computer to run…

DBAOTM Operating systems for the big mainframe box

In the previous posts I have given an overview of the most important mainframe hardware components. In this article I will summarize what operating systems you can run on this hardware. But first… This post appears as part of a number of articles in the category “Don’t Be Afraid Of The Mainframe”. What is actually a mainframe A little late to answer this question, but I thought it was good to address this here. A mainframe is a large computer that is designed to run many different computing tasks at the same time. A mainframe stems from the time where hardware was expensive, and a single central solution for computing was the only way to economically run computing tasks. A lot of characteristics of that design point are still prevalent today. Hence it is good to understand this background. z/OS and Linux, and then some… A number of operating systems can run on the mainframe. I will give a short description here of the operating systems you can run on a mainframe. For the rest of the series of articles I will focus on the two most important ones today. z/OS is the most important mainframe operating system, but also the most different from today’s mainstream operating systems. I will discuss z/OS most extensively.  Linux for the mainframe is the second most important operating system and has gained popularity over the past decade. I will discuss Linux for the mainframe in a separate chapter Linux for the mainframe. z/OS IBM often calls z/OS their flagship mainframe operating system. The roots of z/OS date back to 1964, when the operating system OS/360 was designed for the System/360 computer, the predecessor of IBM’s modern mainframe computers. In the early 70s the successor of the OS/360 operating system was developed, and named MVS (it stands for Multiple Virtual Storage, but you can forget that immediately). MVS has evolved further into OS/390 and now it is called z/OS. The name changes may suggest fundamental different systems, but these are in fact only marketing-driven name changes for MVS and the technology base is still the same, although it has very significantly evolved. z/VM, the mother of all hypervisors z/VM, or VM (VM stands for Virtual Machine) as it was originally named, used to be a full-fledged operating system that was design to run business applications. The operating system included a unique technology that allowed users to virtualize the mainframe hardware and split it up into small virtual machines. Nowadays we have VMWare, KVM, Xen, Hyper-V and others that do the same for x86 and other platforms. But the technology in VM was developed in the 1960s. It was far ahead of it’s time. z/VM can be considered the mother of all hypervisors. z/VM is nowadays it is only still used as a hypervisor for the mainframe, and is no longer as an operating system for business applications. z/VSE The z/VSE operating system is the small brother of z/OS. It was developed in parallel to MVS,…